diff --git a/libraries/liblmdb/.gitignore b/libraries/liblmdb/.gitignore
index d5102a87c0..80b6d81144 100644
--- a/libraries/liblmdb/.gitignore
+++ b/libraries/liblmdb/.gitignore
@@ -5,6 +5,7 @@ mdb_copy
 mdb_stat
 mdb_dump
 mdb_load
+mdb_drop
 *.lo
 *.[ao]
 *.so
diff --git a/libraries/liblmdb/COPYRIGHT b/libraries/liblmdb/COPYRIGHT
index f076556eb5..14eb1493d6 100644
--- a/libraries/liblmdb/COPYRIGHT
+++ b/libraries/liblmdb/COPYRIGHT
@@ -1,4 +1,4 @@
-Copyright 2011-2019 Howard Chu, Symas Corp.
+Copyright 2011-2021 Howard Chu, Symas Corp.
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without
diff --git a/libraries/liblmdb/intro.doc b/libraries/liblmdb/intro.doc
index 64dfcaad84..b5bb06716a 100644
--- a/libraries/liblmdb/intro.doc
+++ b/libraries/liblmdb/intro.doc
@@ -1,5 +1,5 @@
 /*
- * Copyright 2015-2018 Howard Chu, Symas Corp.
+ * Copyright 2015-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/libraries/liblmdb/lmdb.h b/libraries/liblmdb/lmdb.h
index 1f4736ce2b..28cfc36f53 100644
--- a/libraries/liblmdb/lmdb.h
+++ b/libraries/liblmdb/lmdb.h
@@ -136,7 +136,7 @@
  *
  *	@author	Howard Chu, Symas Corporation.
  *
- *	@copyright Copyright 2011-2019 Howard Chu, Symas Corp. All rights reserved.
+ *	@copyright Copyright 2011-2021 Howard Chu, Symas Corp. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted only as authorized by the OpenLDAP
@@ -610,7 +610,7 @@ int  mdb_env_create(MDB_env **env);
 	 *	<li>#MDB_NOTLS
 	 *		Don't use Thread-Local Storage. Tie reader locktable slots to
 	 *		#MDB_txn objects instead of to threads. I.e. #mdb_txn_reset() keeps
-	 *		the slot reseved for the #MDB_txn object. A thread may use parallel
+	 *		the slot reserved for the #MDB_txn object. A thread may use parallel
 	 *		read-only transactions. A read-only transaction may span threads if
 	 *		the user synchronizes its use. Applications that multiplex many
 	 *		user threads over individual OS threads need this option. Such an
@@ -968,7 +968,7 @@ void *mdb_env_get_userctx(MDB_env *env);
 typedef void MDB_assert_func(MDB_env *env, const char *msg);
 
 	/** Set or reset the assert() callback of the environment.
-	 * Disabled if liblmdb is buillt with NDEBUG.
+	 * Disabled if liblmdb is built with NDEBUG.
 	 * @note This hack should become obsolete as lmdb's error handling matures.
 	 * @param[in] env An environment handle returned by #mdb_env_create().
 	 * @param[in] func An #MDB_assert_func function, or 0.
diff --git a/libraries/liblmdb/mdb.c b/libraries/liblmdb/mdb.c
index f68542124e..40728e716b 100644
--- a/libraries/liblmdb/mdb.c
+++ b/libraries/liblmdb/mdb.c
@@ -5,7 +5,7 @@
  *	BerkeleyDB API, but much simplified.
  */
 /*
- * Copyright 2011-2019 Howard Chu, Symas Corp.
+ * Copyright 2011-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -96,6 +96,7 @@ static NtCloseFunc *NtClose;
 #  define SSIZE_MAX	INT_MAX
 # endif
 #endif
+#define MDB_OFF_T	int64_t
 #else
 #include <sys/types.h>
 #include <sys/stat.h>
@@ -108,6 +109,7 @@ static NtCloseFunc *NtClose;
 #include <sys/file.h>
 #endif
 #include <fcntl.h>
+#define MDB_OFF_T	off_t
 #endif
 
 #if defined(__mips) && defined(__linux)
@@ -159,7 +161,10 @@ typedef SSIZE_T	ssize_t;
 #include <resolv.h>	/* defines BYTE_ORDER on HPUX and Solaris */
 #endif
 
-#if defined(__APPLE__) || defined (BSD) || defined(__FreeBSD_kernel__)
+#if defined(__FreeBSD__) && defined(__FreeBSD_version) && __FreeBSD_version >= 1100110
+# define MDB_USE_POSIX_MUTEX	1
+# define MDB_USE_ROBUST	1
+#elif defined(__APPLE__) || defined (BSD) || defined(__FreeBSD_kernel__)
 # if !(defined(MDB_USE_POSIX_MUTEX) || defined(MDB_USE_POSIX_SEM))
 # define MDB_USE_SYSV_SEM	1
 # endif
@@ -585,7 +590,7 @@ static txnid_t mdb_debug_start;
 	 *	The string is printed literally, with no format processing.
 	 */
 #define DPUTS(arg)	DPRINTF(("%s", arg))
-	/** Debuging output value of a cursor DBI: Negative in a sub-cursor. */
+	/** Debugging output value of a cursor DBI: Negative in a sub-cursor. */
 #define DDBI(mc) \
 	(((mc)->mc_flags & C_SUB) ? -(int)(mc)->mc_dbi : (int)(mc)->mc_dbi)
 /** @} */
@@ -1462,9 +1467,12 @@ struct MDB_env {
 	HANDLE		me_fd;		/**< The main data file */
 	HANDLE		me_lfd;		/**< The lock file */
 	HANDLE		me_mfd;		/**< For writing and syncing the meta pages */
-#if defined(MDB_VL32) && defined(_WIN32)
+#ifdef _WIN32
+#ifdef MDB_VL32
 	HANDLE		me_fmh;		/**< File Mapping handle */
-#endif
+#endif /* MDB_VL32 */
+	HANDLE		me_ovfd;	/**< Overlapped/async with write-through file handle */
+#endif /* _WIN32 */
 	/** Failed to update the meta page. Probably an I/O error. */
 #define	MDB_FATAL_ERROR	0x80000000U
 	/** Some fields are initialized. */
@@ -1490,7 +1498,7 @@ struct MDB_env {
 	MDB_txn		*me_txn;		/**< current write transaction */
 	MDB_txn		*me_txn0;		/**< prealloc'd write transaction */
 	mdb_size_t	me_mapsize;		/**< size of the data memory map */
-	off_t		me_size;		/**< current file size */
+	MDB_OFF_T	me_size;		/**< current file size */
 	pgno_t		me_maxpg;		/**< me_mapsize / me_psize */
 	MDB_dbx		*me_dbxs;		/**< array of static DB info */
 	uint16_t	*me_dbflags;	/**< array of flags from MDB_db.md_flags */
@@ -1515,6 +1523,8 @@ struct MDB_env {
 	int		me_live_reader;		/**< have liveness lock in reader table */
 #ifdef _WIN32
 	int		me_pidquery;		/**< Used in OpenProcess */
+	OVERLAPPED	*ov;			/**< Used for for overlapping I/O requests */
+	int		ovs;				/**< Count of OVERLAPPEDs */
 #endif
 #ifdef MDB_USE_POSIX_MUTEX	/* Posix mutexes reside in shared mem */
 #	define		me_rmutex	me_txns->mti_rmutex /**< Shared reader lock */
@@ -1597,7 +1607,7 @@ static int	mdb_page_split(MDB_cursor *mc, MDB_val *newkey, MDB_val *newdata,
 static int  mdb_env_read_header(MDB_env *env, int prev, MDB_meta *meta);
 static MDB_meta *mdb_env_pick_meta(const MDB_env *env);
 static int  mdb_env_write_meta(MDB_txn *txn);
-#ifdef MDB_USE_POSIX_MUTEX /* Drop unused excl arg */
+#if defined(MDB_USE_POSIX_MUTEX) && !defined(MDB_ROBUST_SUPPORTED) /* Drop unused excl arg */
 # define mdb_env_close0(env, excl) mdb_env_close1(env)
 #endif
 static void mdb_env_close0(MDB_env *env, int excl);
@@ -2386,12 +2396,16 @@ mdb_page_dirty(MDB_txn *txn, MDB_page *mp)
 {
 	MDB_ID2 mid;
 	int rc, (*insert)(MDB_ID2L, MDB_ID2 *);
-
-	if (txn->mt_flags & MDB_TXN_WRITEMAP) {
+#ifdef _WIN32	/* With Windows we always write dirty pages with WriteFile,
+				 * so we always want them ordered */
+	insert = mdb_mid2l_insert;
+#else			/* but otherwise with writemaps, we just use msync, we
+				 * don't need the ordering and just append */
+	if (txn->mt_flags & MDB_TXN_WRITEMAP)
 		insert = mdb_mid2l_append;
-	} else {
+	else
 		insert = mdb_mid2l_insert;
-	}
+#endif
 	mid.mid = mp->mp_pgno;
 	mid.mptr = mp;
 	rc = insert(txn->mt_u.dirty_list, &mid);
@@ -2804,7 +2818,11 @@ mdb_env_sync0(MDB_env *env, int force, pgno_t numpgs)
 	int rc = 0;
 	if (env->me_flags & MDB_RDONLY)
 		return EACCES;
-	if (force || !F_ISSET(env->me_flags, MDB_NOSYNC)) {
+	if (force
+#ifndef _WIN32	/* Sync is normally achieved in Windows by doing WRITE_THROUGH writes */
+		|| !(env->me_flags & MDB_NOSYNC)
+#endif
+		) {
 		if (env->me_flags & MDB_WRITEMAP) {
 			int flags = ((env->me_flags & MDB_MAPASYNC) && !force)
 				? MS_ASYNC : MS_SYNC;
@@ -3350,9 +3368,9 @@ mdb_txn_end(MDB_txn *txn, unsigned mode)
 			txn->mt_parent->mt_flags &= ~MDB_TXN_HAS_CHILD;
 			env->me_pgstate = ((MDB_ntxn *)txn)->mnt_pgstate;
 			mdb_midl_free(txn->mt_free_pgs);
-			mdb_midl_free(txn->mt_spill_pgs);
 			free(txn->mt_u.dirty_list);
 		}
+		mdb_midl_free(txn->mt_spill_pgs);
 
 		mdb_midl_free(pghead);
 	}
@@ -3649,21 +3667,30 @@ mdb_page_flush(MDB_txn *txn, int keep)
 	unsigned	psize = env->me_psize, j;
 	int			i, pagecount = dl[0].mid, rc;
 	size_t		size = 0;
-	off_t		pos = 0;
+	MDB_OFF_T	pos = 0;
 	pgno_t		pgno = 0;
 	MDB_page	*dp = NULL;
 #ifdef _WIN32
-	OVERLAPPED	ov;
+	OVERLAPPED	*ov = env->ov;
+	MDB_page	*wdp;
+	int async_i = 0;
+	HANDLE fd = (env->me_flags & MDB_NOSYNC) ? env->me_fd : env->me_ovfd;
 #else
 	struct iovec iov[MDB_COMMIT_PAGES];
+	HANDLE fd = env->me_fd;
+#endif
 	ssize_t		wsize = 0, wres;
-	off_t		wpos = 0, next_pos = 1; /* impossible pos, so pos != next_pos */
+	MDB_OFF_T	wpos = 0, next_pos = 1; /* impossible pos, so pos != next_pos */
 	int			n = 0;
-#endif
 
 	j = i = keep;
-
-	if (env->me_flags & MDB_WRITEMAP) {
+	if (env->me_flags & MDB_WRITEMAP
+#ifdef _WIN32
+		/* In windows, we still do writes to the file (with write-through enabled in sync mode),
+		 * as this is faster than FlushViewOfFile/FlushFileBuffers */
+		&& (env->me_flags & MDB_NOSYNC)
+#endif
+		) {
 		/* Clear dirty flags */
 		while (++i <= pagecount) {
 			dp = dl[i].mptr;
@@ -3678,6 +3705,27 @@ mdb_page_flush(MDB_txn *txn, int keep)
 		goto done;
 	}
 
+#ifdef _WIN32
+	if (pagecount - keep >= env->ovs) {
+		/* ran out of room in ov array, and re-malloc, copy handles and free previous */
+		int ovs = (pagecount - keep) * 1.5; /* provide extra padding to reduce number of re-allocations */
+		int new_size = ovs * sizeof(OVERLAPPED);
+		ov = malloc(new_size);
+		if (ov == NULL)
+			return ENOMEM;
+		int previous_size = env->ovs * sizeof(OVERLAPPED);
+		memcpy(ov, env->ov, previous_size); /* Copy previous OVERLAPPED data to retain event handles */
+		/* And clear rest of memory */
+		memset(&ov[env->ovs], 0, new_size - previous_size);
+		if (env->ovs > 0) {
+			free(env->ov); /* release previous allocation */
+		}
+
+		env->ov = ov;
+		env->ovs = ovs;
+	}
+#endif
+
 	/* Write the pages */
 	for (;;) {
 		if (++i <= pagecount) {
@@ -3695,46 +3743,65 @@ mdb_page_flush(MDB_txn *txn, int keep)
 			size = psize;
 			if (IS_OVERFLOW(dp)) size *= dp->mp_pages;
 		}
-#ifdef _WIN32
-		else break;
-
-		/* Windows actually supports scatter/gather I/O, but only on
-		 * unbuffered file handles. Since we're relying on the OS page
-		 * cache for all our data, that's self-defeating. So we just
-		 * write pages one at a time. We use the ov structure to set
-		 * the write offset, to at least save the overhead of a Seek
-		 * system call.
-		 */
-		DPRINTF(("committing page %"Yu, pgno));
-		memset(&ov, 0, sizeof(ov));
-		ov.Offset = pos & 0xffffffff;
-		ov.OffsetHigh = pos >> 16 >> 16;
-		if (!WriteFile(env->me_fd, dp, size, NULL, &ov)) {
-			rc = ErrCode();
-			DPRINTF(("WriteFile: %d", rc));
-			return rc;
-		}
-#else
 		/* Write up to MDB_COMMIT_PAGES dirty pages at a time. */
-		if (pos!=next_pos || n==MDB_COMMIT_PAGES || wsize+size>MAX_WRITE) {
+		if (pos!=next_pos || n==MDB_COMMIT_PAGES || wsize+size>MAX_WRITE
+#ifdef _WIN32
+			/* If writemap is enabled, consecutive page positions infer
+			 * contiguous (mapped) memory.
+			 * Otherwise force write pages one at a time.
+			 * Windows actually supports scatter/gather I/O, but only on
+			 * unbuffered file handles. Since we're relying on the OS page
+			 * cache for all our data, that's self-defeating. So we just
+			 * write pages one at a time. We use the ov structure to set
+			 * the write offset, to at least save the overhead of a Seek
+			 * system call.
+			 */
+			|| !(env->me_flags & MDB_WRITEMAP)
+#endif
+			) {
 			if (n) {
 retry_write:
 				/* Write previous page(s) */
+				DPRINTF(("committing page %"Z"u", pgno));
+#ifdef _WIN32
+				OVERLAPPED *this_ov = &ov[async_i];
+				/* Clear status, and keep hEvent, we reuse that */
+				this_ov->Internal = 0;
+				this_ov->Offset = wpos & 0xffffffff;
+				this_ov->OffsetHigh = wpos >> 16 >> 16;
+				if (!F_ISSET(env->me_flags, MDB_NOSYNC) && !this_ov->hEvent) {
+					HANDLE event = CreateEvent(NULL, FALSE, FALSE, NULL);
+					if (!event) {
+						rc = ErrCode();
+						DPRINTF(("CreateEvent: %s", strerror(rc)));
+						return rc;
+					}
+					this_ov->hEvent = event;
+				}
+				if (!WriteFile(fd, wdp, wsize, NULL, this_ov)) {
+					rc = ErrCode();
+					if (rc != ERROR_IO_PENDING) {
+						DPRINTF(("WriteFile: %d", rc));
+						return rc;
+					}
+				}
+				async_i++;
+#else
 #ifdef MDB_USE_PWRITEV
-				wres = pwritev(env->me_fd, iov, n, wpos);
+				wres = pwritev(fd, iov, n, wpos);
 #else
 				if (n == 1) {
-					wres = pwrite(env->me_fd, iov[0].iov_base, wsize, wpos);
+					wres = pwrite(fd, iov[0].iov_base, wsize, wpos);
 				} else {
 retry_seek:
-					if (lseek(env->me_fd, wpos, SEEK_SET) == -1) {
+					if (lseek(fd, wpos, SEEK_SET) == -1) {
 						rc = ErrCode();
 						if (rc == EINTR)
 							goto retry_seek;
 						DPRINTF(("lseek: %s", strerror(rc)));
 						return rc;
 					}
-					wres = writev(env->me_fd, iov, n);
+					wres = writev(fd, iov, n);
 				}
 #endif
 				if (wres != wsize) {
@@ -3749,41 +3816,69 @@ mdb_page_flush(MDB_txn *txn, int keep)
 					}
 					return rc;
 				}
+#endif /* _WIN32 */
 				n = 0;
 			}
 			if (i > pagecount)
 				break;
 			wpos = pos;
 			wsize = 0;
+#ifdef _WIN32
+			wdp = dp;
+		}
+#else
 		}
-		DPRINTF(("committing page %"Yu, pgno));
-		next_pos = pos + size;
 		iov[n].iov_len = size;
 		iov[n].iov_base = (char *)dp;
+#endif	/* _WIN32 */
+		DPRINTF(("committing page %"Yu, pgno));
+		next_pos = pos + size;
 		wsize += size;
 		n++;
-#endif	/* _WIN32 */
 	}
 #ifdef MDB_VL32
 	if (pgno > txn->mt_last_pgno)
 		txn->mt_last_pgno = pgno;
 #endif
 
-	/* MIPS has cache coherency issues, this is a no-op everywhere else
-	 * Note: for any size >= on-chip cache size, entire on-chip cache is
-	 * flushed.
-	 */
-	CACHEFLUSH(env->me_map, txn->mt_next_pgno * env->me_psize, DCACHE);
+#ifdef _WIN32
+	if (!F_ISSET(env->me_flags, MDB_NOSYNC)) {
+		/* Now wait for all the asynchronous/overlapped sync/write-through writes to complete.
+		* We start with the last one so that all the others should already be complete and
+		* we reduce thread suspend/resuming (in practice, typically about 99.5% of writes are
+		* done after the last write is done) */
+		rc = 0;
+		while (--async_i >= 0) {
+			if (ov[async_i].hEvent) {
+				if (!GetOverlappedResult(fd, &ov[async_i], &wres, TRUE)) {
+					rc = ErrCode(); /* Continue on so that all the event signals are reset */
+				}
+			}
+		}
+		if (rc) { /* any error on GetOverlappedResult, exit now */
+			return rc;
+		}
+	}
+#endif	/* _WIN32 */
 
-	for (i = keep; ++i <= pagecount; ) {
-		dp = dl[i].mptr;
-		/* This is a page we skipped above */
-		if (!dl[i].mid) {
-			dl[++j] = dl[i];
-			dl[j].mid = dp->mp_pgno;
-			continue;
+	if (!(env->me_flags & MDB_WRITEMAP)) {
+		/* Don't free pages when using writemap (can only get here in NOSYNC mode in Windows)
+		 * MIPS has cache coherency issues, this is a no-op everywhere else
+		 * Note: for any size >= on-chip cache size, entire on-chip cache is
+		 * flushed.
+		 */
+		CACHEFLUSH(env->me_map, txn->mt_next_pgno * env->me_psize, DCACHE);
+
+		for (i = keep; ++i <= pagecount; ) {
+			dp = dl[i].mptr;
+			/* This is a page we skipped above */
+			if (!dl[i].mid) {
+				dl[++j] = dl[i];
+				dl[j].mid = dp->mp_pgno;
+				continue;
+			}
+			mdb_dpage_free(env, dp);
 		}
-		mdb_dpage_free(env, dp);
 	}
 
 done:
@@ -4141,7 +4236,6 @@ mdb_env_init_meta(MDB_env *env, MDB_meta *meta)
 	if (len == -1 && ErrCode() == EINTR) continue; \
 	rc = (len >= 0); break; } while(1)
 #endif
-
 	DPUTS("writing new meta page");
 
 	psize = env->me_psize;
@@ -4180,7 +4274,7 @@ mdb_env_write_meta(MDB_txn *txn)
 	MDB_meta	meta, metab, *mp;
 	unsigned flags;
 	mdb_size_t mapsize;
-	off_t off;
+	MDB_OFF_T off;
 	int rc, len, toggle;
 	char *ptr;
 	HANDLE mfd;
@@ -4202,6 +4296,7 @@ mdb_env_write_meta(MDB_txn *txn)
 	if (mapsize < env->me_mapsize)
 		mapsize = env->me_mapsize;
 
+#ifndef _WIN32 /* We don't want to ever use MSYNC/FlushViewOfFile in Windows */
 	if (flags & MDB_WRITEMAP) {
 		mp->mm_mapsize = mapsize;
 		mp->mm_dbs[FREE_DBI] = txn->mt_dbs[FREE_DBI];
@@ -4217,11 +4312,10 @@ mdb_env_write_meta(MDB_txn *txn)
 			unsigned meta_size = env->me_psize;
 			rc = (env->me_flags & MDB_MAPASYNC) ? MS_ASYNC : MS_SYNC;
 			ptr = (char *)mp - PAGEHDRSZ;
-#ifndef _WIN32	/* POSIX msync() requires ptr = start of OS page */
+			/* POSIX msync() requires ptr = start of OS page */
 			r2 = (ptr - env->me_map) & (env->me_os_psize - 1);
 			ptr -= r2;
 			meta_size += r2;
-#endif
 			if (MDB_MSYNC(ptr, meta_size, rc)) {
 				rc = ErrCode();
 				goto fail;
@@ -4229,6 +4323,7 @@ mdb_env_write_meta(MDB_txn *txn)
 		}
 		goto done;
 	}
+#endif
 	metab.mm_txnid = mp->mm_txnid;
 	metab.mm_last_pg = mp->mm_last_pg;
 
@@ -4379,7 +4474,19 @@ mdb_env_map(MDB_env *env, void *addr)
 		alloctype = MEM_RESERVE;
 	}
 
+	/** Some users are afraid of seeing their disk space getting used
+	 * all at once, so the default is now to do incremental file growth.
+	 * But that has a large performance impact, so give the option of
+	 * allocating the file up front.
+	 */
+#ifdef MDB_FIXEDSIZE
+	LARGE_INTEGER fsize;
+	fsize.LowPart = msize & 0xffffffff;
+	fsize.HighPart = msize >> 16 >> 16;
+	rc = NtCreateSection(&mh, access, NULL, &fsize, secprot, SEC_RESERVE, env->me_fd);
+#else
 	rc = NtCreateSection(&mh, access, NULL, NULL, secprot, SEC_RESERVE, env->me_fd);
+#endif
 	if (rc)
 		return mdb_nt2win32(rc);
 	map = addr;
@@ -4396,22 +4503,27 @@ mdb_env_map(MDB_env *env, void *addr)
 		return mdb_nt2win32(rc);
 	env->me_map = map;
 #else
+	int mmap_flags = MAP_SHARED;
+	int prot = PROT_READ;
+#ifdef MAP_NOSYNC	/* Used on FreeBSD */
+	if (flags & MDB_NOSYNC)
+		mmap_flags |= MAP_NOSYNC;
+#endif
 #ifdef MDB_VL32
 	(void) flags;
-	env->me_map = mmap(addr, NUM_METAS * env->me_psize, PROT_READ, MAP_SHARED,
+	env->me_map = mmap(addr, NUM_METAS * env->me_psize, prot, mmap_flags,
 		env->me_fd, 0);
 	if (env->me_map == MAP_FAILED) {
 		env->me_map = NULL;
 		return ErrCode();
 	}
 #else
-	int prot = PROT_READ;
 	if (flags & MDB_WRITEMAP) {
 		prot |= PROT_WRITE;
 		if (ftruncate(env->me_fd, env->me_mapsize) < 0)
 			return ErrCode();
 	}
-	env->me_map = mmap(addr, env->me_mapsize, prot, MAP_SHARED,
+	env->me_map = mmap(addr, env->me_mapsize, prot, mmap_flags,
 		env->me_fd, 0);
 	if (env->me_map == MAP_FAILED) {
 		env->me_map = NULL;
@@ -4604,7 +4716,7 @@ mdb_fname_init(const char *path, unsigned envflags, MDB_name *fname)
 /** File type, access mode etc. for #mdb_fopen() */
 enum mdb_fopen_type {
 #ifdef _WIN32
-	MDB_O_RDONLY, MDB_O_RDWR, MDB_O_META, MDB_O_COPY, MDB_O_LOCKS
+	MDB_O_RDONLY, MDB_O_RDWR, MDB_O_OVERLAPPED, MDB_O_META, MDB_O_COPY, MDB_O_LOCKS
 #else
 	/* A comment in mdb_fopen() explains some O_* flag choices. */
 	MDB_O_RDONLY= O_RDONLY,                            /**< for RDONLY me_fd */
@@ -4665,6 +4777,11 @@ mdb_fopen(const MDB_env *env, MDB_name *fname,
 	disp = OPEN_ALWAYS;
 	attrs = FILE_ATTRIBUTE_NORMAL;
 	switch (which) {
+	case MDB_O_OVERLAPPED: 	/* for unbuffered asynchronous writes (write-through mode)*/
+		acc = GENERIC_WRITE;
+		disp = OPEN_EXISTING;
+		attrs = FILE_FLAG_OVERLAPPED|FILE_FLAG_WRITE_THROUGH;
+		break;
 	case MDB_O_RDONLY:			/* read-only datafile */
 		acc = GENERIC_READ;
 		disp = OPEN_EXISTING;
@@ -4754,6 +4871,7 @@ mdb_env_open2(MDB_env *env, int prev)
 		if (!NtCreateSection)
 			return MDB_PROBLEM;
 	}
+	env->ovs = 0;
 #endif /* _WIN32 */
 
 #ifdef BROKEN_FDATASYNC
@@ -4880,9 +4998,6 @@ mdb_env_open2(MDB_env *env, int prev)
 #endif
 	env->me_maxpg = env->me_mapsize / env->me_psize;
 
-	if (env->me_txns)
-		env->me_txns->mti_txnid = meta.mm_txnid;
-
 #if MDB_DEBUG
 	{
 		MDB_meta *meta = mdb_env_pick_meta(env);
@@ -4982,6 +5097,9 @@ static int ESECT
 mdb_env_share_locks(MDB_env *env, int *excl)
 {
 	int rc = 0;
+	MDB_meta *meta = mdb_env_pick_meta(env);
+
+	env->me_txns->mti_txnid = meta->mm_txnid;
 
 #ifdef _WIN32
 	{
@@ -5169,7 +5287,7 @@ mdb_env_setup_locks(MDB_env *env, MDB_name *fname, int mode, int *excl)
 	union semun semu;
 #endif
 	int rc;
-	off_t size, rsize;
+	MDB_OFF_T size, rsize;
 
 	rc = mdb_fopen(env, fname, MDB_O_LOCKS, mode, &env->me_lfd);
 	if (rc) {
@@ -5500,6 +5618,11 @@ mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode
 		mode, &env->me_fd);
 	if (rc)
 		goto leave;
+#ifdef _WIN32
+	rc = mdb_fopen(env, &fname, MDB_O_OVERLAPPED, mode, &env->me_ovfd);
+	if (rc)
+		goto leave;
+#endif
 
 	if ((flags & (MDB_RDONLY|MDB_NOLOCK)) == MDB_RDONLY) {
 		rc = mdb_env_setup_locks(env, &fname, mode, &excl);
@@ -5508,10 +5631,10 @@ mdb_env_open(MDB_env *env, const char *path, unsigned int flags, mdb_mode_t mode
 	}
 
 	if ((rc = mdb_env_open2(env, flags & MDB_PREVSNAPSHOT)) == MDB_SUCCESS) {
+		/* Synchronous fd for meta writes. Needed even with
+		 * MDB_NOSYNC/MDB_NOMETASYNC, in case these get reset.
+		 */
 		if (!(flags & (MDB_RDONLY|MDB_WRITEMAP))) {
-			/* Synchronous fd for meta writes. Needed even with
-			 * MDB_NOSYNC/MDB_NOMETASYNC, in case these get reset.
-			 */
 			rc = mdb_fopen(env, &fname, MDB_O_META, mode, &env->me_mfd);
 			if (rc)
 				goto leave;
@@ -5618,6 +5741,16 @@ mdb_env_close0(MDB_env *env, int excl)
 	}
 	if (env->me_mfd != INVALID_HANDLE_VALUE)
 		(void) close(env->me_mfd);
+#ifdef _WIN32
+	if (env->ovs > 0) {
+		for (i = 0; i < env->ovs; i++) {
+			CloseHandle(env->ov[i].hEvent);
+		}
+		free(env->ov);
+	}
+	if (env->me_ovfd != INVALID_HANDLE_VALUE)
+		(void) close(env->me_ovfd);
+#endif
 	if (env->me_fd != INVALID_HANDLE_VALUE)
 		(void) close(env->me_fd);
 	if (env->me_txns) {
@@ -5665,6 +5798,17 @@ mdb_env_close0(MDB_env *env, int excl)
 			if (excl > 0)
 				semctl(env->me_rmutex->semid, 0, IPC_RMID);
 		}
+#elif defined(MDB_ROBUST_SUPPORTED)
+		/* If we have the filelock:  If we are the
+		 * only remaining user, clean up robust
+		 * mutexes.
+		 */
+		if (excl == 0)
+			mdb_env_excl_lock(env, &excl);
+		if (excl > 0) {
+			pthread_mutex_destroy(env->me_txns->mti_rmutex);
+			pthread_mutex_destroy(env->me_txns->mti_wmutex);
+		}
 #endif
 		munmap((void *)env->me_txns, (env->me_maxreaders-1)*sizeof(MDB_reader)+sizeof(MDB_txninfo));
 	}
@@ -6804,16 +6948,12 @@ mdb_cursor_next(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op)
 
 	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 		mdb_xcursor_init1(mc, leaf);
-	}
-	if (data) {
+		rc = mdb_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
+		if (rc != MDB_SUCCESS)
+			return rc;
+	} else if (data) {
 		if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
 			return rc;
-
-		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
-			rc = mdb_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
-			if (rc != MDB_SUCCESS)
-				return rc;
-		}
 	}
 
 	MDB_GET_KEY(leaf, key);
@@ -6837,7 +6977,8 @@ mdb_cursor_prev(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op)
 
 	mp = mc->mc_pg[mc->mc_top];
 
-	if (mc->mc_db->md_flags & MDB_DUPSORT) {
+	if ((mc->mc_db->md_flags & MDB_DUPSORT) &&
+		mc->mc_ki[mc->mc_top] < NUMKEYS(mp)) {
 		leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
 		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 			if (op == MDB_PREV || op == MDB_PREV_DUP) {
@@ -6879,27 +7020,25 @@ mdb_cursor_prev(MDB_cursor *mc, MDB_val *key, MDB_val *data, MDB_cursor_op op)
 	DPRINTF(("==> cursor points to page %"Yu" with %u keys, key index %u",
 	    mdb_dbg_pgno(mp), NUMKEYS(mp), mc->mc_ki[mc->mc_top]));
 
+	if (!IS_LEAF(mp))
+		return MDB_CORRUPTED;
+
 	if (IS_LEAF2(mp)) {
 		key->mv_size = mc->mc_db->md_pad;
 		key->mv_data = LEAF2KEY(mp, mc->mc_ki[mc->mc_top], key->mv_size);
 		return MDB_SUCCESS;
 	}
 
-	mdb_cassert(mc, IS_LEAF(mp));
 	leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
 
 	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 		mdb_xcursor_init1(mc, leaf);
-	}
-	if (data) {
+		rc = mdb_cursor_last(&mc->mc_xcursor->mx_cursor, data, NULL);
+		if (rc != MDB_SUCCESS)
+			return rc;
+	} else if (data) {
 		if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
 			return rc;
-
-		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
-			rc = mdb_cursor_last(&mc->mc_xcursor->mx_cursor, data, NULL);
-			if (rc != MDB_SUCCESS)
-				return rc;
-		}
 	}
 
 	MDB_GET_KEY(leaf, key);
@@ -7057,24 +7196,22 @@ mdb_cursor_set(MDB_cursor *mc, MDB_val *key, MDB_val *data,
 
 	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
 		mdb_xcursor_init1(mc, leaf);
-	}
-	if (data) {
-		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
-			if (op == MDB_SET || op == MDB_SET_KEY || op == MDB_SET_RANGE) {
-				rc = mdb_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
+		if (op == MDB_SET || op == MDB_SET_KEY || op == MDB_SET_RANGE) {
+			rc = mdb_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
+		} else {
+			int ex2, *ex2p;
+			if (op == MDB_GET_BOTH) {
+				ex2p = &ex2;
+				ex2 = 0;
 			} else {
-				int ex2, *ex2p;
-				if (op == MDB_GET_BOTH) {
-					ex2p = &ex2;
-					ex2 = 0;
-				} else {
-					ex2p = NULL;
-				}
-				rc = mdb_cursor_set(&mc->mc_xcursor->mx_cursor, data, NULL, MDB_SET_RANGE, ex2p);
-				if (rc != MDB_SUCCESS)
-					return rc;
+				ex2p = NULL;
 			}
-		} else if (op == MDB_GET_BOTH || op == MDB_GET_BOTH_RANGE) {
+			rc = mdb_cursor_set(&mc->mc_xcursor->mx_cursor, data, NULL, MDB_SET_RANGE, ex2p);
+			if (rc != MDB_SUCCESS)
+				return rc;
+		}
+	} else if (data) {
+		if (op == MDB_GET_BOTH || op == MDB_GET_BOTH_RANGE) {
 			MDB_val olddata;
 			MDB_cmp_func *dcmp;
 			if ((rc = mdb_node_read(mc, leaf, &olddata)) != MDB_SUCCESS)
@@ -7132,22 +7269,23 @@ mdb_cursor_first(MDB_cursor *mc, MDB_val *key, MDB_val *data)
 	mc->mc_ki[mc->mc_top] = 0;
 
 	if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
-		key->mv_size = mc->mc_db->md_pad;
-		key->mv_data = LEAF2KEY(mc->mc_pg[mc->mc_top], 0, key->mv_size);
+		if ( key ) {
+			key->mv_size = mc->mc_db->md_pad;
+			key->mv_data = LEAF2KEY(mc->mc_pg[mc->mc_top], 0, key->mv_size);
+		}
 		return MDB_SUCCESS;
 	}
 
-	if (data) {
-		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
-			mdb_xcursor_init1(mc, leaf);
-			rc = mdb_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
-			if (rc)
-				return rc;
-		} else {
-			if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
-				return rc;
-		}
+	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+		mdb_xcursor_init1(mc, leaf);
+		rc = mdb_cursor_first(&mc->mc_xcursor->mx_cursor, data, NULL);
+		if (rc)
+			return rc;
+	} else if (data) {
+		if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
+			return rc;
 	}
+
 	MDB_GET_KEY(leaf, key);
 	return MDB_SUCCESS;
 }
@@ -7176,21 +7314,21 @@ mdb_cursor_last(MDB_cursor *mc, MDB_val *key, MDB_val *data)
 	leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
 
 	if (IS_LEAF2(mc->mc_pg[mc->mc_top])) {
-		key->mv_size = mc->mc_db->md_pad;
-		key->mv_data = LEAF2KEY(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top], key->mv_size);
+		if (key) {
+			key->mv_size = mc->mc_db->md_pad;
+			key->mv_data = LEAF2KEY(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top], key->mv_size);
+		}
 		return MDB_SUCCESS;
 	}
 
-	if (data) {
-		if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
-			mdb_xcursor_init1(mc, leaf);
-			rc = mdb_cursor_last(&mc->mc_xcursor->mx_cursor, data, NULL);
-			if (rc)
-				return rc;
-		} else {
-			if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
-				return rc;
-		}
+	if (F_ISSET(leaf->mn_flags, F_DUPDATA)) {
+		mdb_xcursor_init1(mc, leaf);
+		rc = mdb_cursor_last(&mc->mc_xcursor->mx_cursor, data, NULL);
+		if (rc)
+			return rc;
+	} else if (data) {
+		if ((rc = mdb_node_read(mc, leaf, data)) != MDB_SUCCESS)
+			return rc;
 	}
 
 	MDB_GET_KEY(leaf, key);
@@ -7352,6 +7490,7 @@ mdb_cursor_get(MDB_cursor *mc, MDB_val *key, MDB_val *data,
 			rc = MDB_NOTFOUND;
 			break;
 		}
+		mc->mc_flags &= ~C_EOF;
 		{
 			MDB_node *leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
 			if (!F_ISSET(leaf->mn_flags, F_DUPDATA)) {
@@ -7666,7 +7805,7 @@ mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data,
 						offset *= 4; /* space for 4 more */
 						break;
 					}
-					/* FALLTHRU: Big enough MDB_DUPFIXED sub-page */
+					/* FALLTHRU */ /* Big enough MDB_DUPFIXED sub-page */
 				case MDB_CURRENT:
 					fp->mp_flags |= P_DIRTY;
 					COPY_PGNO(fp->mp_pgno, mp->mp_pgno);
@@ -7865,7 +8004,7 @@ mdb_cursor_put(MDB_cursor *mc, MDB_val *key, MDB_val *data,
 			xdata.mv_size = 0;
 			xdata.mv_data = "";
 			leaf = NODEPTR(mc->mc_pg[mc->mc_top], mc->mc_ki[mc->mc_top]);
-			if (flags == MDB_CURRENT) {
+			if ((flags & (MDB_CURRENT|MDB_APPENDDUP)) == MDB_CURRENT) {
 				xflags = MDB_CURRENT|MDB_NOSPILL;
 			} else {
 				mdb_xcursor_init1(mc, leaf);
@@ -7969,6 +8108,8 @@ mdb_cursor_del(MDB_cursor *mc, unsigned int flags)
 		return rc;
 
 	mp = mc->mc_pg[mc->mc_top];
+	if (!IS_LEAF(mp))
+		return MDB_CORRUPTED;
 	if (IS_LEAF2(mp))
 		goto del_key;
 	leaf = NODEPTR(mp, mc->mc_ki[mc->mc_top]);
@@ -9347,60 +9488,68 @@ mdb_cursor_del0(MDB_cursor *mc)
 		}
 	}
 	rc = mdb_rebalance(mc);
+	if (rc)
+		goto fail;
 
-	if (rc == MDB_SUCCESS) {
-		/* DB is totally empty now, just bail out.
-		 * Other cursors adjustments were already done
-		 * by mdb_rebalance and aren't needed here.
-		 */
-		if (!mc->mc_snum)
-			return rc;
+	/* DB is totally empty now, just bail out.
+	 * Other cursors adjustments were already done
+	 * by mdb_rebalance and aren't needed here.
+	 */
+	if (!mc->mc_snum) {
+		mc->mc_flags |= C_EOF;
+		return rc;
+	}
 
-		mp = mc->mc_pg[mc->mc_top];
-		nkeys = NUMKEYS(mp);
+	mp = mc->mc_pg[mc->mc_top];
+	nkeys = NUMKEYS(mp);
 
-		/* Adjust other cursors pointing to mp */
-		for (m2 = mc->mc_txn->mt_cursors[dbi]; !rc && m2; m2=m2->mc_next) {
-			m3 = (mc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
-			if (! (m2->mc_flags & m3->mc_flags & C_INITIALIZED))
-				continue;
-			if (m3->mc_snum < mc->mc_snum)
-				continue;
-			if (m3->mc_pg[mc->mc_top] == mp) {
-				/* if m3 points past last node in page, find next sibling */
-				if (m3->mc_ki[mc->mc_top] >= mc->mc_ki[mc->mc_top]) {
-					if (m3->mc_ki[mc->mc_top] >= nkeys) {
-						rc = mdb_cursor_sibling(m3, 1);
-						if (rc == MDB_NOTFOUND) {
-							m3->mc_flags |= C_EOF;
-							rc = MDB_SUCCESS;
-							continue;
-						}
+	/* Adjust other cursors pointing to mp */
+	for (m2 = mc->mc_txn->mt_cursors[dbi]; !rc && m2; m2=m2->mc_next) {
+		m3 = (mc->mc_flags & C_SUB) ? &m2->mc_xcursor->mx_cursor : m2;
+		if (!(m2->mc_flags & m3->mc_flags & C_INITIALIZED))
+			continue;
+		if (m3->mc_snum < mc->mc_snum)
+			continue;
+		if (m3->mc_pg[mc->mc_top] == mp) {
+			if (m3->mc_ki[mc->mc_top] >= mc->mc_ki[mc->mc_top]) {
+			/* if m3 points past last node in page, find next sibling */
+				if (m3->mc_ki[mc->mc_top] >= nkeys) {
+					rc = mdb_cursor_sibling(m3, 1);
+					if (rc == MDB_NOTFOUND) {
+						m3->mc_flags |= C_EOF;
+						rc = MDB_SUCCESS;
+						continue;
 					}
-					if (mc->mc_db->md_flags & MDB_DUPSORT) {
-						MDB_node *node = NODEPTR(m3->mc_pg[m3->mc_top], m3->mc_ki[m3->mc_top]);
-						/* If this node has dupdata, it may need to be reinited
-						 * because its data has moved.
-						 * If the xcursor was not initd it must be reinited.
-						 * Else if node points to a subDB, nothing is needed.
-						 * Else (xcursor was initd, not a subDB) needs mc_pg[0] reset.
-						 */
-						if (node->mn_flags & F_DUPDATA) {
-							if (m3->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED) {
-								if (!(node->mn_flags & F_SUBDATA))
-									m3->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(node);
-							} else {
-								mdb_xcursor_init1(m3, node);
-								m3->mc_xcursor->mx_cursor.mc_flags |= C_DEL;
-							}
+					if (rc)
+						goto fail;
+				}
+				if (m3->mc_xcursor && !(m3->mc_flags & C_EOF)) {
+					MDB_node *node = NODEPTR(m3->mc_pg[m3->mc_top], m3->mc_ki[m3->mc_top]);
+					/* If this node has dupdata, it may need to be reinited
+					 * because its data has moved.
+					 * If the xcursor was not initd it must be reinited.
+					 * Else if node points to a subDB, nothing is needed.
+					 * Else (xcursor was initd, not a subDB) needs mc_pg[0] reset.
+					 */
+					if (node->mn_flags & F_DUPDATA) {
+						if (m3->mc_xcursor->mx_cursor.mc_flags & C_INITIALIZED) {
+							if (!(node->mn_flags & F_SUBDATA))
+								m3->mc_xcursor->mx_cursor.mc_pg[0] = NODEDATA(node);
+						} else {
+							mdb_xcursor_init1(m3, node);
+							rc = mdb_cursor_first(&m3->mc_xcursor->mx_cursor, NULL, NULL);
+							if (rc)
+								goto fail;
 						}
 					}
+					m3->mc_xcursor->mx_cursor.mc_flags |= C_DEL;
 				}
 			}
 		}
-		mc->mc_flags |= C_DEL;
 	}
+	mc->mc_flags |= C_DEL;
 
+fail:
 	if (rc)
 		mc->mc_txn->mt_flags |= MDB_TXN_ERROR;
 	return rc;
diff --git a/libraries/liblmdb/mdb_copy.1 b/libraries/liblmdb/mdb_copy.1
index 30e4754f13..c61a102424 100644
--- a/libraries/liblmdb/mdb_copy.1
+++ b/libraries/liblmdb/mdb_copy.1
@@ -1,5 +1,5 @@
 .TH MDB_COPY 1 "2017/07/31" "LMDB 0.9.70"
-.\" Copyright 2012-2019 Howard Chu, Symas Corp. All Rights Reserved.
+.\" Copyright 2012-2021 Howard Chu, Symas Corp. All Rights Reserved.
 .\" Copying restrictions apply.  See COPYRIGHT/LICENSE.
 .SH NAME
 mdb_copy \- LMDB environment copy tool
diff --git a/libraries/liblmdb/mdb_copy.c b/libraries/liblmdb/mdb_copy.c
index 23be815062..ecc9beeff0 100644
--- a/libraries/liblmdb/mdb_copy.c
+++ b/libraries/liblmdb/mdb_copy.c
@@ -1,6 +1,6 @@
 /* mdb_copy.c - memory-mapped database backup tool */
 /*
- * Copyright 2012-2018 Howard Chu, Symas Corp.
+ * Copyright 2012-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/libraries/liblmdb/mdb_drop.1 b/libraries/liblmdb/mdb_drop.1
index 10666e5204..959a8e96b7 100644
--- a/libraries/liblmdb/mdb_drop.1
+++ b/libraries/liblmdb/mdb_drop.1
@@ -1,5 +1,5 @@
 .TH MDB_DROP 1 "2017/11/19" "LMDB 0.9.70"
-.\" Copyright 2014-2018 Howard Chu, Symas Corp. All Rights Reserved.
+.\" Copyright 2014-2021 Howard Chu, Symas Corp. All Rights Reserved.
 .\" Copying restrictions apply.  See COPYRIGHT/LICENSE.
 .SH NAME
 mdb_drop \- LMDB database delete tool
diff --git a/libraries/liblmdb/mdb_drop.c b/libraries/liblmdb/mdb_drop.c
index 7d2af4b62e..c6b82dd269 100644
--- a/libraries/liblmdb/mdb_drop.c
+++ b/libraries/liblmdb/mdb_drop.c
@@ -1,6 +1,6 @@
 /* mdb_drop.c - memory-mapped database delete tool */
 /*
- * Copyright 2016-2018 Howard Chu, Symas Corp.
+ * Copyright 2016-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/libraries/liblmdb/mdb_dump.1 b/libraries/liblmdb/mdb_dump.1
index 424ad9321c..ad733c9e57 100644
--- a/libraries/liblmdb/mdb_dump.1
+++ b/libraries/liblmdb/mdb_dump.1
@@ -1,5 +1,5 @@
 .TH MDB_DUMP 1 "2017/07/31" "LMDB 0.9.70"
-.\" Copyright 2014-2017 Howard Chu, Symas Corp. All Rights Reserved.
+.\" Copyright 2014-2021 Howard Chu, Symas Corp. All Rights Reserved.
 .\" Copying restrictions apply.  See COPYRIGHT/LICENSE.
 .SH NAME
 mdb_dump \- LMDB environment export tool
diff --git a/libraries/liblmdb/mdb_dump.c b/libraries/liblmdb/mdb_dump.c
index b7737f12de..29ee02e031 100644
--- a/libraries/liblmdb/mdb_dump.c
+++ b/libraries/liblmdb/mdb_dump.c
@@ -1,6 +1,6 @@
 /* mdb_dump.c - memory-mapped database dump tool */
 /*
- * Copyright 2011-2018 Howard Chu, Symas Corp.
+ * Copyright 2011-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -64,6 +64,8 @@ static void text(MDB_val *v)
 	end = c + v->mv_size;
 	while (c < end) {
 		if (isprint(*c)) {
+			if (*c == '\\')
+				putchar('\\');
 			putchar(*c);
 		} else {
 			putchar('\\');
@@ -179,7 +181,7 @@ int main(int argc, char *argv[])
 	 * -V: print version and exit
 	 * (default) dump only the main DB
 	 */
-	while ((i = getopt(argc, argv, "af:lnps:V")) != EOF) {
+	while ((i = getopt(argc, argv, "af:lnps:vV")) != EOF) {
 		switch(i) {
 		case 'V':
 			printf("%s\n", MDB_VERSION_STRING);
diff --git a/libraries/liblmdb/mdb_load.1 b/libraries/liblmdb/mdb_load.1
index a2f8373c57..78439a14da 100644
--- a/libraries/liblmdb/mdb_load.1
+++ b/libraries/liblmdb/mdb_load.1
@@ -1,5 +1,5 @@
 .TH MDB_LOAD 1 "2015/09/30" "LMDB 0.9.17"
-.\" Copyright 2014-2018 Howard Chu, Symas Corp. All Rights Reserved.
+.\" Copyright 2014-2021 Howard Chu, Symas Corp. All Rights Reserved.
 .\" Copying restrictions apply.  See COPYRIGHT/LICENSE.
 .SH NAME
 mdb_load \- LMDB environment import tool
diff --git a/libraries/liblmdb/mdb_load.c b/libraries/liblmdb/mdb_load.c
index ad911c088c..6f6dddc9e6 100644
--- a/libraries/liblmdb/mdb_load.c
+++ b/libraries/liblmdb/mdb_load.c
@@ -1,6 +1,6 @@
 /* mdb_load.c - memory-mapped database load tool */
 /*
- * Copyright 2011-2018 Howard Chu, Symas Corp.
+ * Copyright 2011-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -236,7 +236,7 @@ static int readline(MDB_val *out, MDB_val *buf)
 		while (c2 < end) {
 			if (*c2 == '\\') {
 				if (c2[1] == '\\') {
-					c1++; c2 += 2;
+					*c1++ = *c2;
 				} else {
 					if (c2+3 > end || !isxdigit(c2[1]) || !isxdigit(c2[2])) {
 						Eof = 1;
@@ -244,8 +244,8 @@ static int readline(MDB_val *out, MDB_val *buf)
 						return EOF;
 					}
 					*c1++ = unhex(++c2);
-					c2 += 2;
 				}
+				c2 += 2;
 			} else {
 				/* copies are redundant when no escapes were used */
 				*c1++ = *c2++;
diff --git a/libraries/liblmdb/mdb_stat.1 b/libraries/liblmdb/mdb_stat.1
index 83988a0fa0..e1e37550ad 100644
--- a/libraries/liblmdb/mdb_stat.1
+++ b/libraries/liblmdb/mdb_stat.1
@@ -1,5 +1,5 @@
 .TH MDB_STAT 1 "2017/07/31" "LMDB 0.9.70"
-.\" Copyright 2012-2019 Howard Chu, Symas Corp. All Rights Reserved.
+.\" Copyright 2012-2021 Howard Chu, Symas Corp. All Rights Reserved.
 .\" Copying restrictions apply.  See COPYRIGHT/LICENSE.
 .SH NAME
 mdb_stat \- LMDB environment status tool
diff --git a/libraries/liblmdb/mdb_stat.c b/libraries/liblmdb/mdb_stat.c
index 08f30befd6..088f620a19 100644
--- a/libraries/liblmdb/mdb_stat.c
+++ b/libraries/liblmdb/mdb_stat.c
@@ -1,6 +1,6 @@
 /* mdb_stat.c - memory-mapped database status tool */
 /*
- * Copyright 2011-2018 Howard Chu, Symas Corp.
+ * Copyright 2011-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -65,7 +65,7 @@ int main(int argc, char *argv[])
 	 * -V: print version and exit
 	 * (default) print stat of only the main DB
 	 */
-	while ((i = getopt(argc, argv, "Vaefnrs:")) != EOF) {
+	while ((i = getopt(argc, argv, "Vaefnrs:v")) != EOF) {
 		switch(i) {
 		case 'V':
 			printf("%s\n", MDB_VERSION_STRING);
diff --git a/libraries/liblmdb/midl.c b/libraries/liblmdb/midl.c
index ee89822e39..568daba1e8 100644
--- a/libraries/liblmdb/midl.c
+++ b/libraries/liblmdb/midl.c
@@ -3,8 +3,8 @@
 /* $OpenLDAP$ */
 /* This work is part of OpenLDAP Software <http://www.openldap.org/>.
  *
- * Copyright 2000-2019 The OpenLDAP Foundation.
- * Portions Copyright 2001-2018 Howard Chu, Symas Corp.
+ * Copyright 2000-2021 The OpenLDAP Foundation.
+ * Portions Copyright 2001-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/libraries/liblmdb/midl.h b/libraries/liblmdb/midl.h
index 0f826771a1..1035c01e14 100644
--- a/libraries/liblmdb/midl.h
+++ b/libraries/liblmdb/midl.h
@@ -11,8 +11,8 @@
 /* $OpenLDAP$ */
 /* This work is part of OpenLDAP Software <http://www.openldap.org/>.
  *
- * Copyright 2000-2019 The OpenLDAP Foundation.
- * Portions Copyright 2001-2019 Howard Chu, Symas Corp.
+ * Copyright 2000-2021 The OpenLDAP Foundation.
+ * Portions Copyright 2001-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/libraries/liblmdb/mtest.c b/libraries/liblmdb/mtest.c
index 6fc5840c3f..c03daa1081 100644
--- a/libraries/liblmdb/mtest.c
+++ b/libraries/liblmdb/mtest.c
@@ -1,6 +1,6 @@
 /* mtest.c - memory-mapped database tester/toy */
 /*
- * Copyright 2011-2018 Howard Chu, Symas Corp.
+ * Copyright 2011-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/libraries/liblmdb/mtest2.c b/libraries/liblmdb/mtest2.c
index 64b742aa46..1ce4c9442d 100644
--- a/libraries/liblmdb/mtest2.c
+++ b/libraries/liblmdb/mtest2.c
@@ -1,6 +1,6 @@
 /* mtest2.c - memory-mapped database tester/toy */
 /*
- * Copyright 2011-2018 Howard Chu, Symas Corp.
+ * Copyright 2011-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/libraries/liblmdb/mtest3.c b/libraries/liblmdb/mtest3.c
index 81e4bbf9b0..f8da0d331c 100644
--- a/libraries/liblmdb/mtest3.c
+++ b/libraries/liblmdb/mtest3.c
@@ -1,6 +1,6 @@
 /* mtest3.c - memory-mapped database tester/toy */
 /*
- * Copyright 2011-2018 Howard Chu, Symas Corp.
+ * Copyright 2011-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/libraries/liblmdb/mtest4.c b/libraries/liblmdb/mtest4.c
index c355cf105a..3d7476c455 100644
--- a/libraries/liblmdb/mtest4.c
+++ b/libraries/liblmdb/mtest4.c
@@ -1,6 +1,6 @@
 /* mtest4.c - memory-mapped database tester/toy */
 /*
- * Copyright 2011-2018 Howard Chu, Symas Corp.
+ * Copyright 2011-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/libraries/liblmdb/mtest5.c b/libraries/liblmdb/mtest5.c
index 95793ec1fb..d7a7307e29 100644
--- a/libraries/liblmdb/mtest5.c
+++ b/libraries/liblmdb/mtest5.c
@@ -1,6 +1,6 @@
 /* mtest5.c - memory-mapped database tester/toy */
 /*
- * Copyright 2011-2018 Howard Chu, Symas Corp.
+ * Copyright 2011-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/libraries/liblmdb/mtest6.c b/libraries/liblmdb/mtest6.c
index cb0d4d73c9..cf8ba961d0 100644
--- a/libraries/liblmdb/mtest6.c
+++ b/libraries/liblmdb/mtest6.c
@@ -1,6 +1,6 @@
 /* mtest6.c - memory-mapped database tester/toy */
 /*
- * Copyright 2011-2018 Howard Chu, Symas Corp.
+ * Copyright 2011-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/libraries/liblmdb/sample-bdb.txt b/libraries/liblmdb/sample-bdb.txt
index 97220f0ed2..8ca927c6cf 100644
--- a/libraries/liblmdb/sample-bdb.txt
+++ b/libraries/liblmdb/sample-bdb.txt
@@ -3,7 +3,7 @@
  * Do a line-by-line comparison of this and sample-mdb.txt
  */
 /*
- * Copyright 2012-2018 Howard Chu, Symas Corp.
+ * Copyright 2012-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
diff --git a/libraries/liblmdb/sample-mdb.txt b/libraries/liblmdb/sample-mdb.txt
index 1d20ed3d02..2e1731631d 100644
--- a/libraries/liblmdb/sample-mdb.txt
+++ b/libraries/liblmdb/sample-mdb.txt
@@ -3,7 +3,7 @@
  * Do a line-by-line comparison of this and sample-bdb.txt
  */
 /*
- * Copyright 2012-2018 Howard Chu, Symas Corp.
+ * Copyright 2012-2021 Howard Chu, Symas Corp.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without